The Galaxy is a Crowded Place – A Series

One of the things that mankind’s search for exoplanets – planets located outside our own solar system – has shown us is that there are a lot more of them out there than we initially thought.

As of this morning, we've found 1,774 exoplanets, a good chunk of them (962) found by the Kepler mission! They have a backlog of about 3,845 planet candidates for it to work through. Way back in 1989, we found the first exoplanet – HD114762 b (nicknamed Latham’s Planet, after its discoverer) – because of its great mass (10.98 Jupiter masses). That mass causes it to exert a small tug on its star due to its radial velocity, making the star “wobble”. HD114762 b is situated 128.7 light years from Earth, with a surface temperature of about 487K.

So, I thought it would be fascinating to explore our galactic neighborhood, beginning with those closest to us, working our way further into the galaxy.

Of course, as many of us know, that means we’ll start with Alpha Centauri B b:

For long-time Star Trek fans, it probably won’t come as a surprise that we found a planet around the closest star to us. They probably will be surprised by how recently that discovery happened – two years ago in 2012! Alpha Centauri B b is interesting because it’s an Earth-mass planet (1.13 Earth masses) extremely close to its star (only .0400 AU) away. That means it whips around its star (1.227 solar masses), with a very short year (3.23 days)! It makes sense that we found this planet by the same radial velocity “wobble” indicator as referenced above. Alpha Centauri B b is 4.37 light years from Earth, and is, so far, the only planet in its system.

Well, that’s it for this time! A huge part of my decision to keep the series going will be reader feedback. If it’s something you find useful, entertaining, or informative, please let me know here in the thread! If noone’s digging it but me, I’ll get that message quickly.

Please keep it up. I am excited about this thread. There are so many discoveries it will be interesting to put them in some order. I think it would be interesting if you mentioned planets that are in the "habitable zone" around a star.

Funny, when I watched the debut episode of "Space: 1999" during the late 70s (not during its initial run), I thought to myself, "Oh, brother! There's no way we could detect a planet orbiting a distant star, well, not with 20th Century technology." This was my response to the subplot about Earth launching a manned expedition to the planet "Meta". And yet, in reality, we did just that, with 11 years to spare! And now, only 14 years into the 21st Century, we've listed nearly eighteen hundred! That is mind blowing! Even more amazing, some of these are rocky worlds not much larger than our own. Gas giants that make Jupiter whimper from inadequacy, yeah, I can more easily grasp how we'd detect those, but something only 10,000 miles wide or smaller, tens if not hundreds of lightyears distant...D*mn!

Welcome back. As of today, we’re up to 1,776 exoplanets, and next on our list for the series is epsilon Eridani b:

Epsilon Eridani b orbits its gas giant star about 10.44 light years from Earth, at a distance of 3.39 AUs from that host star, and has a 2,502-day year. Its surface temperature is 111.8 K. As of right now, it’s the only known planet in its system, and was discovered quite recently in 2000. It was found using the same radial velocity technique as was Alpha Centauri B b, as it was measured exerting a gravitational tug on Epsilon Eridani, a K2 V-type star.

As far as supporting life, due to its distance from its type of star (3.39 AU), it is well beyond the “Goldilocks Zone” there – which is between .65 – 1.21 AU from the star. Sadly, this means no life as we know it can exist on Epsilon Eridani b.

Thanks so much for the feedback thus far! It’s clear that you guys are enjoying it as much as I am, so I’ll soldier on with the series. Keep in mind the structure of it is to start with our closest planets and works its way out into the galaxy. Maybe I will consider supplementing that with a bit on exoplanets in the news or some other topical information.

This time we’ll be taking a slight detour on our trip through the galaxy, on our search for exoplanets, in what is proving to be a very crowded galaxy. Just a week ago, I would have been making a very different kind of post in my series to highlight the exoplanets that are the closest to our star. But due to the rapid advance of science, a new discovery was announced just a few days ago that has changed that.

What is it?

The answer is Kapteyn b. Kapteyn’s star is named – as is tradition – after its discover, the Dutch astronomer Jacobus Kapteyn. There are several qualities about Kapteyn b that make it special: 1) Its proximity to Earth, which is 12.75 light years, and 2) Its age, which is roughly 11 billion years old. To put it into perspective, the Earth is about 5 billion years old. Life on Kapteyn b has had twice as long to evolve, 3) Its mass is 4.8 Earth masses, which puts it into the category of super-earths, 4) Its orbit around its M1.0 type star is 48.62 days, which puts it within its Goldilocks zone of .07-.15 AUs. This delicate combination of qualities make Kapteyn a place which should keep our attention for a long time to come.

Kapteyn b isn’t alone in its system. We have - so far - found a second planet, called Kapteyn c, another super earth that is 7.0 Earth masses, orbits further away – 121 days - from its host star, and thus, too far outside of its habitable zone to support life as we know it.

Both Kapteyn b and Kapteyn c were found in 2014 using the tried and true radial velocity method.